The long-term goal of this research proposal is to define the clinical significance of right ventricular infarction. Four major questions form the rationale for this proposed research investigation: (1) How do single and combined non-invasive methods compare to a biplane oblique cineangiographic technique for assessing right ventricular size and performance? (2) Can non-invasive techniques identify and quantify the extent of right ventricular infarction? (3) What is the incidence, course and prognosis of hemodynamically significant right ventricular infarction? (4) Are vasodilator and inotropic agents therapeutically beneficial in patients with right ventricular infarction? The important specific studies designed to address these clinical questions are: (1) The comparative accuracy of non-invasive techniques for estimating right ventricular size and performance will be determined by comparison to similar measures obtained by a validated biplane oblique cineangiographic method. (2) The incidence of hemodynamically significant right ventricular infarction will be determined prospectively by performing right heart catheterization with repeat pressure and cardiac output measurements during volume administration in patients with acute inferior transmural myocardial infarction. (3) The ability to identify accurately a hemodynamically significant right ventricular infarction and to assess its resultant effect on right ventricular size and performance will be evaluated non-invasively using: first-transit and gated equilibrium radionuclide angiography, two-dimensional echocardiography, and technetium 99m pyrophosphate myocardial scintigraphy. (4) The course and prognosis of patients with right ventricular infarction will be determined by clinical evaluation and by repeat invasive and non-invasive studies during the year following infarction. (5) The efficacy of nitroprusside infusion and digitalis administration for improving right ventricular systolic performance in patients with hemodynamically significant acute right ventricular infarction will be assessed by repeat hemodynamic measurements and by serial non-invasive studies. Therefore, these studies will provide new information concerning non-invasive methods and the diagnosis, course and prognosis and treatment of right ventricular infarction.